This invention relates to matrix transformers, and in particular to matrix transformers having multiple turn primaries, either single coil windings as for a full bridge, half bridge or forward converter or multiple coil windings as for push-pull windings, split windings or a forward converter having a reset winding.
FIG. 1 shows a prior art magnetic core 1 as may be used to make a matrix transformer. FIG. 2 shows a phantom view 4 of the magnetic core 1 of FIG. 1 further comprising first and second secondary windings 2 and 3. FIG. 3 shows a prior are “element” 5 of a matrix transformer comprising a pair of magnetic cores 1, 1 which are the magnetic core 1 of FIG. 1 each further comprising first and second secondary windings 2 and 3. The secondary windings 2 and 3 may be connected in various arrangements as required by a particular application.
FIG. 4 shows a prior art matrix transformer 10 comprising five magnetic elements 5—5 which are the magnetic element 5 of FIG. 3. A primary winding 11 is wound by hand through the five elements 5—5 of the matrix transformer 10. Winding the primary winding 11 is a labor intensive manual operation. It is time consuming and requires considerable skill, yet the result is often messy. If the wires of the primary winding 11 cross in the matrix transformer 10, it can be difficult or impossible to get the required number of turns, and their arrangement is somewhat random yielding inconsistent product.
FIG. 5 shows a prior art printed circuit winding 15 for a matrix transformer, and FIG. 6 shows the printed circuit winding 15 installed in a matrix transformer 20. A plurality of terminal pins 21—21 connect the printed circuit winding to a mother board, both to complete the turns around the end of the matrix transformer 20 and for connection to external circuitry. This arrangement has several problems. On is that the vias in the printed circuit winding occupy space that restricts the conductor area of conductors that must pass the vias. Another is the current crowding that occurs at the via. Also, usually a number of the turns of the primary winding just wrap around the transformer, not requiring any termination, yet every turn of the printed circuit winding 15 is connected through the mother board.